Simple reflection and leaky waves in the vicinity of a line of exceptionalbulk waves

A study is made of the existence of two-component solutions of the reflecti on problem (simple reflection) and of leaky wave solutions in the vicinity of a line of exceptional bulk waves in a semi-infinite medium of arbitrary anisotropy. The line of exceptional waves is assumed to be associated with a Type 1 transonic state. It is found that generally one, three, and five s imple reflections may appear, depending on the number of non-degenerate uni form partial modes at the transonic state. In the three-dimensional space o f orientation angles specifying the geometry of the boundary-value problem, the set of configurations allowing simple reflection occupies two-dimensio nal surfaces. These surfaces pass through the line of exceptional waves. Le aky waves are shown to appear only near transonic states where there are tw o non-degenerate uniform partial modes, and their 'geometries' of propagati on occupy two sectors confined between the surfaces of simple reflection. A criterion for the existence of leaky waves is derived. As an illustration of the general considerations, simple reflection and leaky waves in hexagon al media near the transverse isotropic direction are discussed. (C) 1999 El sevier Science B.V. All rights reserved.